1. Field of Invention
The present invention relates to safety brakes and, more specifically, to a safety brake device applied to theatre hoists that lift and maintain heavy loads suspended.
2. Description of Prior Art
Hoists that lift loads in a vertical direction are used in many industries for a variety of applications. For theatrical settings, athletic and entertainment arenas, overhead lifting with higher safety standards are routinely required because hoists are lifting loads directly over human beings. It is also common for portions of the staging in these theatrical settings to be lifted. Similar safety standards are required in these instances because people may be standing on the portion of the stage being lifted.
Live performances in a theater typically employ a number of curtains and backdrops to convey to the audience different settings, environments, moods, and the like. These curtains and backdrops must be changed throughout the course of a performance within a fairly short time frame without interrupting the performance. Typically this is done by raising a particular backdrop above the stage and out of sight of the audience when it is not being used. When a particular backdrop is needed, it is lowered into place on the stage.
Theatrical backdrops and curtains are typically suspended from battens, which are pipes or trusses that span the width of the stage. Battens can be 20 feet or more in length, depending on the size of the stage. As should be apparent, the weight of the battens and the items suspended from them can have substantial weight. As the weight of the load increases so does the power required to raise the load. Counterweights are employed to balance the load of the batten and its associated load. However, if the load is not closely balanced or if there is a failure in the motorized drive lifting the hoist, the system may get out of control, dropping the load or the counter-weight, causing injury or death to people nearby and/or collateral damage.
Therefore, because of the risk of hoist failure, there is a need for a safety device to prevent the uncontrolled release of heavy loads and staging that are either supported above or below human beings.